Write the equation for the parabola that has x− intercepts (−2,0) and (1.2,0) and y− intercept (0,−4).

Question

Write the equation for the parabola that has x− intercepts (−2,0) and (1.2,0) and y− intercept (0,−4).

Please tell me the equasion and not how to get it.

Answer 1

You know that y=0 at the two x-intercepts, so start with

y = A [x - (-2)] (x - 1.2)

y = A(x + 2)(x - 1.2)

At the y-intercept,

-4 = A(0 + 2)(0 - 1.2)

-4 = -2.4A

A = 4/2.4 = 5/3

y = (5/3)(x + 2)(x - 1.2)